1. Field of the Invention
This invention relates to ultrasonic acoustic imaging, primarily for medical purposes.
2. Brief Description of the Background Art
Ultrasonic acoustic imaging finds many uses, particularly in the field of non-invasive medical testing. Direct detection of the emitted acoustic frequency permits, for example, prenatal fetal imaging. Detection of Doppler shifted acoustic frequencies permits observation of flow of a particle-containing liquid, for example, blood flow. Acoustic imaging equipment utilizes a probe that is applied to the skin of the patient overlying the part of the body being investigated. At the end of the probe is an array of transducers, usually piezoelectric, that are excited by bursts of electrical energy at the ultrasonic frequency and modulated to transmit pulses of ultrasonic energy into the body region being investigated. The subsurface structures reflect some of that energy, either at the transmitted frequency or Doppler shifted, back to the probe, where it is detected by piezoelectric receiver elements in the probe. One application of this technology to the three dimensional mapping and tracking of blood flow is disclosed in parent U.S. application Ser. No. 09/926,666, which issued on Jan. 27, 2004 as U.S. Pat. No. 6,682,483. The pertinent text of that application is included herein below.